Teams upset by a hot issue (5)
I believe the answer is:
steam
'a hot issue' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'teams upset' is the wordplay.
'upset' indicates anagramming the letters.
'teams' anagrammed gives 'STEAM'.
'by' acts as a link.
Can you help me to learn more?
(Other definitions for steam that I've seen before include "Sort of water" , "Form of water" , "Vapour; energy" , "Cook" , "Like old radio" .)